Waterproofing coatings are frequently applied to the outer surface of concrete foundation walls to prevent water penetration through the wall. By definition, a "waterproofing" coating is one that will prevent the passage of water when the water present in the soil is under hydrostatic pressure. In contrast, a "damp-proofing" coating is one which is not intended to be impermeable when the water in the soil is under pressure. An extremely effective waterproofing coating is that described in U.S. Pat. No. 5,352,531. The coating of that patent is a highly adhesive, elastomeric type which is asphalt free and when cured is of nonhazardous and nontoxic. The coating, preferably applied to the foundation wall by spraying, provides an elastic, highly adhesive, water impervious membrane that firmly adheres to the foundation wall to prevent penetration of water through the wall even when the wall is subjected to substantial hydrostatic pressure, up to about 90 pounds per square foot, or more.
After application of the elastomeric coating to the foundation wall, the wall is backfilled normally through use of mechanical handling equipment, such as a bulldozer. It has been found that during backfilling, solid material such as coarse rocks and stones, scrap lumber, sheet metal, and other materials may be forced against the wall and may rupture the elastomeric coating, with the result that the water impermeable characteristics of the coating may be destroyed. Because of this, it is recommended to apply protection board over the elastomeric coating. The protection board is applied to the tacky coating and will firmly bond to the coating. The protection board as used in the past, is not in itself a waterproofing membrane. A common type of protection board as used in the past, is polystyrene foam board The polystyrene foam board aids in protecting the elastomeric coating and has some insulating value. However, the polystyrene foam is somewhat brittle and can be fractured by backfilling. Further, the polystyrene foam is not waterproof and over time will absorb water so that the protection board, in itself does not constitute a waterproofing membrane.
U.S. Pat. No. 5,511,346 describes a foundation wall construction utilizing a thermoplastic foam insulation and drainage board. In accordance with that patent, the outer surface of the foam insulation board is provided with a series of parallel flow channels each channel having a narrow inlet at the outer surface of the board and a wider portion in the interior of the board. The patent states that the channels aid in providing water drainage downward to the drain tile at the footing. However, with the construction as shown in U.S. Pat. No. 5,511,346, the channels cannot be placed too closely together without destroying the physical integrity of the foam board. If the channels are located too closely together, the thin area between channels is susceptible to damage and breakage during backfilling.